Question

Hey, could anyone check my answer?

Define the terms (a) prototroph and (b) auxotroph. If you were given an E.
coli strain that was growing on nutrient agar how in practice would you
determine whether or not it is a prototroph or an auxotroph and how would
you determine what if any growth requirements it has. On the basis that cys is
the short code for amino acid cysteine and str is the abbreviation for the
antibiotic streptomycin how would confirm the properties of a strain that is
Cys-
StrR
.
(I dont have enough space, so I will write in the answer box)

Answer 1

a) Prototroph - 'wild type' bacteria, which requires only minimum medium, containing only inorganic salts, water and carbon source, for its growth and division.
b) Autotroph - 'mutant' type bacteria, which requires a special medium for its growth and division, for example, a medium which contains adenine or biotine. Autotroph 'mutants' are usually obtained from prototroph cultures.

I would determine if this E. coli culture is autotroph or prototroph by growing it on minimum medium, which contains only water, glucose and sodium chloride - as it is minimum medium, autotroph culture wouldnt be able to grow (I AM NOT SURE ABOUT THIS!)

Also, to determine if this culture is \[cis ^{-}\] and \[str ^{R}\] I would NOT add cysteine to the medium and see if the culture grows, as cis- culture requires cysteine added. For strR, the there would be antiobitic streptomycin added, to check if the culture is resistant to this antibiotic.

Answer 2

@MrNood could you please have a look?

Answer 3

@Abhisar I know you will know if I get the question correctly: }}}

Answer 4

Not my area of expertise I'm sorry.

Answer 5

that's ok, thanks anyway:)

Answer 6

and I made a huge mistake - it should have been 'auxotroph' instead of autotroph!

Answer 7

@Compassionate maybe you could help me?

Answer 8

@anonymous_user ah, maybe you?

Answer 9

@BioEpic maybe?

Answer 10

NICE! This is correct!
For
"I would determine if this E. coli culture is autotroph or prototroph by growing it on minimum medium, which contains only water, glucose and sodium chloride - as it is minimum medium, autotroph culture wouldnt be able to grow (I AM NOT SURE ABOUT THIS!)"
You are correct. You should plate the auxotroph and prototroph there; the auxotroph will not grow because it is missing a part in a metabolic pathway and needs one or more extra supplements.

Just make sure you don't confuse 'auxotrophs' and 'autotrophs' or it will be marked wrong :)

I hope this helped!

Answer 11

thanks a lot, Bio! Yeah, I know: }}} I dunno why I got confused about those, because I know what th

Answer 12

what they are*

Answer 13

No problem! If you ever need help with things like this, just let me know. I am doing these kind of experiments (though a lot more complicated, with vectors and casein and chymosin expression. If I can't understand the question *I'm only 13* I will ask a molecular biology expert whose job is to do these kind of things.

Answer 14

wow, super! best of luck!!!!

Answer 15

Lol. Good luck in your future studies!!

Answer 16

An `auxotroph` needs some nutrient that the `wild type strain (prototroph)` can make for itself. For example, a trp- auxotroph can’t make its own tryptophan (an amino acid). To grow trp- bacteria, you need to add tryptophan to the growth medium. Prototrophs are trp+; they don’t need any tryptophan supplied since they make their own.



So yes in order to determine, you should grow the E.coli strain in a `minimum medium`. If the culture is successful, then they are Prototroph else they must be Auxotroph.

Answer 17

Good job both @BioEpic and @Kamille !

Answer 18

Thanks!!